This application claims, under 35 USC 119, priority of Japanese Application No. 2000-98419 filed Mar. 31, 2000.
1. Field of the Invention
The present inventions relate to fuel cells and fuel cell devices.
2. Description of the Prior Art
Today, fuel cells are attracting attention as an energy source for the next generation. A fuel cell has two kinds of electrodes, a fuel electrode and an oxygen electrode, and generates electricity by oxidizing fuel at its fuel electrode and reducing oxygen at its oxygen electrode.
Therefore, an object of the present inventions is to provide fuel cells and fuel cell devices having improved cell output.
The present invention is directed to a fuel cell, comprising:
a fuel electrode which has a fuel-diffusion layer for diffusing fuel;
an oxygen electrode which has an oxygen-diffusion layer for diffusing oxygen; and
an electrolyte layer which is arranged between the fuel electrode and the oxygen electrode, wherein the fuel-diffusion layer has higher water-repellency than that of the oxygen-diffusion layer.
Another aspect of the present invention is directed to a fuel cell, comprising:
a fuel electrode which has a fuel-diffusion layer for diffusing fuel and a fuel-reactive layer for reaction of the fuel, the fuel-reactive layer being in contact with the fuel-diffusion layer;
an oxygen electrode which has an oxygen-diffusion layer for diffusing oxygen and an oxygen-reactive layer for reaction of the oxygen, the oxygen-reactive layer being in contact with the oxygen-diffusion layer; and
an electrolyte layer which is arranged between the fuel electrode and the oxygen electrode, wherein the fuel-diffusion layer has higher water-repellency than that of the oxygen-diffusion layer.
According to the present invention described above, cell output of fuel cells can be enhanced.
In this invention, it is preferred that each of the fuel-diffusion layer and the oxygen-diffusion layer has at least one water-repellent-material-containing sublayer which contains a material having water repellency, and that the water-repellent-material-containing sublayer of the fuel-diffusion layer has higher water-repellency than that of the oxygen-diffusion layer. In this case, it is preferred that the content of the material having water repellency in the water-repellent-material-containing layer of the fuel-diffusion layer is larger, most preferably at least 5 wt. % larger, than that of the material having water repellency in the water-repellent-material-containing sublayer of the oxygen-diffusion layer.
It is also preferred that the content of the water-repellent material is 20 to 80 wt. % in the water-repellent-material-containing sublayer of the fuel-diffusion layer.
The content of the water-repellent material is preferably 15 to 65 wt. % in the water-repellent-material-containing sublayer of the oxygen-diffusion layer.
It is also preferred that the water-repellent-material-containing sublayer of the fuel-diffusion layer and the water-repellent-material-containing sublayer of the oxygen-diffusion layer both contain a conductive material, and that the conductive material in the water-repellent-material-containing sublayer of the fuel-diffusion layer has higher water-repellency than that of the conductive material in the water-repellent -material-containing sublayer of the oxygen-diffusion layer.
It is also preferred that the water-repellent-material-containing sublayer is a layer in which the water repellency material is carried by a particulate conductive material.
Still further, in this invention, it is also preferred that the fuel-diffusion layer has water-repellent-material-containing sublayers at both its sides.
It is also preferred that the oxygen-diffusion layer has water-repellent-material-containing sublayers at both its sides.
Further, the water contact angle on the surface of the fuel-diffusion layer is preferably larger than the water contact angle on the surface of the oxygen-diffusion layer by at least 5xc2x0.
It is also preferred that the water contact angle on the surface of the fuel-diffusion layer is 100 to 160xc2x0 and that on the surface of the oxygen-diffusion layer is 90 to 150xc2x0.
It is preferred that the fuel cell uses hydrogen as fuel.
Another aspect of the present invention is directed to a fuel cell device, comprising a fuel cell as described above.
Further, another aspect of the present invention is directed to a fuel cell device, comprising:
a fuel cell main body which includes
(a) a fuel electrode which has a fuel-diffusion layer for diffusing fuel;
(b) an oxygen electrode which has an oxygen-diffusion layer for diffusing oxygen, the fuel-diffusion layer having higher water-repellency than that of the oxygen-diffusion layer; and
(c) an electrolyte layer between the fuel electrode and the oxygen electrode; fuel supply means for supplying fuel to the fuel electrode; and
oxygen supply means for supplying gas containing oxygen gas to the oxygen electrode.
Preferably, the fuel cell device further comprises water supply means for supplying water to the oxygen electrode.
These and other objects, structures and advantages will be readily apparent from the following description of the preferred embodiments and examples taken in conjunction with the accompanying drawings.